Medical devices that deliver a therapy to a patient often do so according to a program that includes a plurality of parameters. Each of the parameters of such a program defines an aspect of the therapy as delivered by the medical device according to that program. For example, the programs used by medical devices that deliver therapy in the form of electrical stimulation, such as neurostimulators, typically include parameters that define characteristics of the electrical stimulation waveform to be delivered. Where electrical stimulation is delivered in the form of electrical pulses, for example, the parameters for such a program may include a voltage or current amplitude, a pulse width, and a rate at which the pulses are to be delivered by the medical device. Further, where a medical device that delivers electrical stimulation is implantable and, as is typical for implantable neurostimulators, coupled to an electrode set including a plurality of electrodes, such a program may include an indication of the particular electrodes within the electrode set to be used to deliver the pulses, and the polarities of the selected electrodes. As another example, the programs used by medical devices that deliver therapy via infusion of a drug or other agent may include parameters that define flow rates, agent types or concentrations, and infusion type, e.g., continuous or bolus.
In most cases, a clinician creates the one or more programs that a medical device will use to deliver therapy to a patient during an initial programming session. In the case of implantable medical devices, the initial programming session typically occurs shortly after the device is implanted in the patient. The values for each of the parameters of a program may have a significant impact on the efficacy and side effects of the delivery of therapy according to that program. The process of selecting values for the parameters that provide adequate results can be time consuming. In particular, the process may require a great deal of trial-and-error testing of numerous potential combinations of parameter values before a “best” program is discovered. A “best” program may be a program that is better in terms of clinic efficacy versus side effects experienced than other programs tested. The process is particularly burdensome in the case of programming implantable neurostimulators for delivery of spinal cord stimulation therapy, which are often coupled to an electrode set including eight or sixteen electrodes. The number of possible combinations of electrodes that could be tested during a programming session from a set of that size is substantial, e.g., potentially on the order of tens or hundreds of thousands, or even millions of possible electrode combinations.
In some cases, the clinician may test combinations of parameter values, i.e., potential programs, by manually specifying each combination to test based on intuition or some idiosyncratic methodology, and recording notes on the efficacy and side effects of each combination after delivery of stimulation according to that combination. During a programming session, the clinician may be required to make notations describing the parameters of a number of tested programs and feedback received from the patient regarding the perceived efficacy or side effects of each program. The clinician may then select one or more “best” programs based on the notations.
Even after this often-lengthy process, the programs selected during an initial programming session may ultimately prove to be inadequate. The eventual inadequacy of the initial programming may be due to a variety of problems, including progression of symptoms and/or an underlying ailment, increased or changed symptoms or side effects during activities and/or postures that were not replicated in the clinic during the initial programming session, slow onset of side effects and, in the case of delivery of stimulation via electrodes located on implantable leads, lead migration. If the programs selected during an initial programming session prove to be inadequate, the patient must return to the clinic for a follow-up programming session. Multiple follow-up programming sessions may be required over the period of time that the medical device is used to deliver therapy to the patient.